This invention relates to a process for thermal conversion of organic matter primarily into gaseous and vapor forms and, in particular, to an improved continuous process and apparatus for thermal conversion of rubber vehicle tires and the like utilizing a molten lead bath to yield gaseous and vapor forms that may be further treated to recover useful hydrocarbon liquids.
The need for efficient and ever-improving methods of disposal of waste products has long existed. Modern realizations have shown the need to handle waste products in an environmentally sound manner. Historically, landfills have been utilized as the least expensive manner for disposal, since landfill usage normally requires no more than the collection and transport of the material to the site. This procedure has been followed in many areas which still have sufficient open areas available. However, several factors preclude the employment of landfills. Less and less space now exists in many countries, particularly in and adjacent to urban areas, which areas obviously generate the greatest volume of waste material. Additionally, ever increasing environmental controls are forcing many jurisdictions to seek alternate means for waste disposal, as landfills pollute underlying water tables, etc.
In the case of inorganic matter, it is known to recycle many materials such as glass and metals and the processes for handling these offer little environmental concern. On the other hand, the disposal of waste organic matter has been known to raise many objections. In a landfill, many waste organic materials may decompose and yield harmful products capable of contaminating the soil and ground water. Other organic wastes (such as vehicle tires and the myriad of plastic products) exhibit little or no decomposition in a landfill and, more importantly, are difficult to bury. These latter wastes, in view of their resiliency, tend to work their way to the surface of any manipulated landfill. Many dumps devoted exclusively to tires are located throughout the country--some containing several million tires each. When such tire dumps catch on fire, it often takes weeks to extinguish the smoldering blaze, if it can be extinguished at all, with a most objectionable emission of pollutants usually spreading over tens of thousands of acres.
Several states and other jurisdictions have totally outlawed any landfills. This action dictates that new means must be provided to accommodate the disposal of at least those organic materials which heretofore mostly have been relegated to a landfill or the like. With over 200 million tires being used annually in this country alone, it follows that any disposal method which can utilize tires as an infeed and which yields valuable by-products, will present a unique advancement of the art.
The concept of using molten metal, including lead, for the thermal conversion of organic matter is generally known. Molten metal has been utilized in the distillation of granular wood or coal by submerging the granules in a molten metal bath and passing the granules through the bath, sandwiched between two endless screens. The prior art has not suggested a continuous processing method wherein organic waste material of varying configurations, such as scrap tires, is evaporated in the absence of oxygen and converted to a gaseous state with an extremely high degree of efficiency, both as to speed of processing as well as to the value of the collected hydrocarbons.